These include where the terminally ill person was clearly shown to have been in sound mind, and if the person helping them kill themselves reported the suicide to the police immediately.

However the changes came with a host of limitations, including a strict ban on any medical professional engaging in assisted suicide. The guidelines were introduced with close relatives of the terminally ill in mind, where that person had made a "clear and settled wish" to die.

Leading the debate Tory MP Richard Ottoway told MPs: "This is a very sensitive area of law which evokes deep emotions.

"The House is not being asked to support assisted dying for the terminally ill, which requires a change in the law on assisted suicide.

"Assisted suicide will remain a criminal offence. This is a debate on the application of existing law of England, Wales and Northern Ireland. There are many differing positions, but Parliament and not the courts should decide the policy."

Some MPs are pushing for the government to consult on putting the DPP's guidelines on a statutory legal footing. Many more are seeking to amend the backbench business motion to place an emphasis on better palliative care.

Tory MP Fiona Bruce has an amendment to the motion which would call for greater specialist palliative care and hospice provision - she opposes any further relaxation of the assisted suicide laws or regulations. She told MPs that Britain already had excellent palliative care, and claimed that in jurisdictions where assisted suicide laws had been brought in, the number of those taking their own life had climbed dramatically.

The government believes assisted suicide is matter of conscience for MPs and not political parties, so there is no whip on MPs during the debate, which is likely to continue until around seven o'clock.

However ministers favour retaining the existing model of guidelines for the CPS not written into law, believing this allows for flexibility in an area which has "infinite" scenarios.